[Qemu-devel] [PATCH] Add a DTrace tracing backend targetted for SystemTAP compatability

[Daniel P. Berrange]

This introduces a new tracing backend that targets the SystemTAP
implementation of DTrace userspace tracing. The core functionality
should be applicable and standard across any DTrace implementation
on Solaris, OS-X, *BSD, but the Makefile rules will likely need
some small additional changes to cope with OS specific build
requirements.

This backend builds a little differently from the other tracing
backends. Specifically there is no 'trace.c' file, because the
'dtrace' command line tool generates a '.o' file directly from
the dtrace probe definition file. The probe definition is usually
named with a '.d' extension but QEMU uses '.d' files for its
external makefile dependancy tracking, so this uses '.dtrace' as
the extension for the probe definition file.

The 'tracetool' program gains the ability to generate a trace.h
file for DTrace, and also to generate the trace.d file containing
the dtrace probe definition, and finally a qemu.stp file which is
a wrapper around the probe definition providing more convenient
access from SystemTAP scripts.

eg, instead of

  probe process("qemu").mark("qemu_malloc") {
    printf("Malloc %d %p\n", $arg1, $arg2);
  }

The addition of qemu.stp to /usr/share/systemtap/tapset/
lets users write

  probe qemu.qemu_malloc {
    printf("Malloc %d %p\n", size, ptr);
  }

* .gitignore: Ignore trace-dtrace.*
* Makefile: Extra rules for generating DTrace files
* Makefile.obj: Don't build trace.o for DTrace, use
  trace-dtrace.o generated by 'dtrace' instead
* tracetool: Support for generating DTrace/SystemTAP
  data files

Signed-off-by: Daniel P. Berrange <address@hidden>
---
 .gitignore    |    3 +
 Makefile      |   31 ++++++++++
 Makefile.objs |    4 +
 tracetool     |  175 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 211 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index a43e4d1..0d27afd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,9 @@ config-host.*
 config-target.*
 trace.h
 trace.c
+trace-dtrace.h
+trace-dtrace.dtrace
+qemu.stp
 *-timestamp
 *-softmmu
 *-darwin-user
diff --git a/Makefile b/Makefile
index 252c817..812b0d3 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,9 @@
 # Makefile for QEMU.
 
 GENERATED_HEADERS = config-host.h trace.h
+ifeq ($(TRACE_BACKEND),dtrace)
+GENERATED_HEADERS += trace-dtrace.h
+endif
 
 ifneq ($(wildcard config-host.mak),)
 # Put the all: rule here so that config-host.mak can contain dependencies.
@@ -106,7 +109,11 @@ ui/vnc.o: QEMU_CFLAGS += $(VNC_TLS_CFLAGS)
 
 bt-host.o: QEMU_CFLAGS += $(BLUEZ_CFLAGS)
 
+ifeq ($(TRACE_BACKEND),dtrace)
+trace.h: trace.h-timestamp trace-dtrace.h
+else
 trace.h: trace.h-timestamp
+endif
 trace.h-timestamp: $(SRC_PATH)/trace-events config-host.mak
        $(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -h < 
$< > $@,"  GEN   trace.h")
        @cmp -s $@ trace.h || cp $@ trace.h
@@ -118,6 +125,23 @@ trace.c-timestamp: $(SRC_PATH)/trace-events config-host.mak
 
 trace.o: trace.c $(GENERATED_HEADERS)
 
+trace-dtrace.h: trace-dtrace.dtrace
+       $(call quiet-command,dtrace -o $@ -h -s $<, "  GEN   trace-dtrace.h")
+
+# Normal practice is to name DTrace probe file with a '.d' extension
+# but that gets picked up by QEMU's Makefile as an external dependancy
+# rule file. So we use '.dtrace' instead
+trace-dtrace.dtrace: trace-dtrace.dtrace-timestamp
+trace-dtrace.dtrace-timestamp: $(SRC_PATH)/trace-events config-host.mak
+       $(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -d < 
$< > $@,"  GEN   trace-dtrace.dtrace")
+       @cmp -s $@ trace-dtrace.dtrace || cp $@ trace-dtrace.dtrace
+ifdef CONFIG_LINUX
+       $(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -s < 
$< > qemu.stp,"  GEN   qemu.stp")
+endif
+
+trace-dtrace.o: trace-dtrace.dtrace $(GENERATED_HEADERS)
+       $(call quiet-command,dtrace -o $@ -G -s $<, "  GEN trace-dtrace.o")
+
 simpletrace.o: simpletrace.c $(GENERATED_HEADERS)
 
 version.o: $(SRC_PATH)/version.rc config-host.mak
@@ -154,6 +178,7 @@ clean:
        rm -f slirp/*.o slirp/*.d audio/*.o audio/*.d block/*.o block/*.d 
net/*.o net/*.d fsdev/*.o fsdev/*.d ui/*.o ui/*.d
        rm -f qemu-img-cmds.h
        rm -f trace.c trace.h trace.c-timestamp trace.h-timestamp
+       rm -f trace-dtrace.dtrace trace-dtrace.h trace-dtrace.h-timestamp 
qemu.stp
        $(MAKE) -C tests clean
        for d in $(ALL_SUBDIRS) libhw32 libhw64 libuser libdis libdis-user; do \
        if test -d $$d; then $(MAKE) -C $$d $@ || exit 1; fi; \
@@ -214,6 +239,12 @@ ifneq ($(BLOBS),)
                $(INSTALL_DATA) $(SRC_PATH)/pc-bios/$$x "$(DESTDIR)$(datadir)"; 
\
        done
 endif
+ifeq ($(TRACE_BACKEND),dtrace)
+ifdef CONFIG_LINUX
+       $(INSTALL_DIR) "$(DESTDIR)$(datadir)/../systemtap/tapset"
+       $(INSTALL_DATA) qemu.stp "$(DESTDIR)$(datadir)/../systemtap/tapset"
+endif
+endif
        $(INSTALL_DIR) "$(DESTDIR)$(datadir)/keymaps"
        set -e; for x in $(KEYMAPS); do \
                $(INSTALL_DATA) $(SRC_PATH)/pc-bios/keymaps/$$x 
"$(DESTDIR)$(datadir)/keymaps"; \
diff --git a/Makefile.objs b/Makefile.objs
index 816194a..ccecda0 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -273,10 +273,14 @@ libdis-$(CONFIG_SPARC_DIS) += sparc-dis.o
 ######################################################################
 # trace
 
+ifeq ($(TRACE_BACKEND),dtrace)
+trace-obj-y = trace-dtrace.o
+else
 trace-obj-y = trace.o
 ifeq ($(TRACE_BACKEND),simple)
 trace-obj-y += simpletrace.o
 endif
+endif
 
 vl.o: QEMU_CFLAGS+=$(GPROF_CFLAGS)
 
diff --git a/tracetool b/tracetool
index 7010858..59b66fd 100755
--- a/tracetool
+++ b/tracetool
@@ -20,10 +20,13 @@ Backends:
   --nop     Tracing disabled
   --simple  Simple built-in backend
   --ust     LTTng User Space Tracing backend
+  --dtrace  DTrace/SystemTAP backend
 
 Output formats:
   -h    Generate .h file
   -c    Generate .c file
+  -d    Generate .d file (DTrace only)
+  -s    Generate .stp file (DTrace with SystemTAP only)
 EOF
     exit 1
 }
@@ -68,6 +71,31 @@ get_argnames()
     fi
 }
 
+# Get the argument name list of a trace event
+get_arglist()
+{
+    local nfields field name
+    nfields=0
+    for field in $(get_args "$1"); do
+        nfields=$((nfields + 1))
+
+        # Drop pointer star
+        field=${field#\*}
+
+        # Only argument names have commas at the end
+        name=${field%,}
+        test "$field" = "$name" && continue
+
+        printf "%s" "$name "
+    done
+
+    # Last argument name
+    if [ "$nfields" -gt 1 ]
+    then
+        printf "%s" "$name"
+    fi
+}
+
 # Get the number of arguments to a trace event
 get_argc()
 {
@@ -306,6 +334,127 @@ EOF
     echo "}"
 }
 
+linetoh_begin_dtrace()
+{
+    cat <<EOF
+#include "trace-dtrace.h"
+EOF
+}
+
+linetoh_dtrace()
+{
+    local name args state
+    name=$(get_name "$1")
+    args=$(get_args "$1")
+    argnames=$(get_argnames "$1")
+    state=$(get_state "$1")
+    if [ "$state" = "0" ] ; then
+        name=${name##disable }
+    fi
+
+    nameupper=`echo $name | tr '[:lower:]' '[:upper:]'`
+
+    # Define an empty function for the trace event
+    cat <<EOF
+static inline void trace_$name($args) {
+  if (QEMU_${nameupper}_ENABLED())
+    QEMU_${nameupper}($argnames);
+}
+EOF
+}
+
+linetoh_end_dtrace()
+{
+    return
+}
+
+linetoc_begin_dtrace()
+{
+    return
+}
+
+linetoc_dtrace()
+{
+    # No need for function definitions in dtrace backend
+    return
+}
+
+linetoc_end_dtrace()
+{
+    return
+}
+
+linetod_begin_dtrace()
+{
+    cat <<EOF
+provider qemu {
+EOF
+}
+
+linetod_dtrace()
+{
+    local name args state
+    name=$(get_name "$1")
+    args=$(get_args "$1")
+    state=$(get_state "$1")
+    if [ "$state" = "0" ] ; then
+        name=${name##disable }
+    fi
+
+    # Define prototype for probe arguments
+    cat <<EOF
+        probe $name($args);
+EOF
+}
+
+linetod_end_dtrace()
+{
+    cat <<EOF
+};
+EOF
+}
+
+linetos_begin_dtrace()
+{
+    return
+}
+
+linetos_dtrace()
+{
+    local name args argnames state
+    name=$(get_name "$1")
+    args=$(get_args "$1")
+    arglist=$(get_arglist "$1")
+    state=$(get_state "$1")
+    if [ "$state" = "0" ] ; then
+        name=${name##disable }
+    fi
+
+    # Define prototype for probe arguments
+    cat <<EOF
+probe qemu.$name = process("qemu").mark("$name")
+{
+EOF
+
+    i=1
+    for arg in $arglist
+    do
+        cat <<EOF
+  $arg = \$arg$i;
+EOF
+       i="$((i+1))"
+    done
+
+    cat <<EOF
+}
+EOF
+}
+
+linetos_end_dtrace()
+{
+    return
+}
+
 # Process stdin by calling begin, line, and end functions for the backend
 convert()
 {
@@ -326,7 +475,7 @@ convert()
         if test -z "$disable"; then
             # Pass the disabled state as an arg to lineto$1_simple().
             # For all other cases, call lineto$1_nop()
-            if [ $backend = "simple" ]; then
+            if [ $backend = "simple" -o "$backend" = "dtrace" ]; then
                 "$process_line" "$str"
             else
                 "lineto$1_nop" "${str##disable }"
@@ -360,9 +509,29 @@ tracetoc()
     convert c
 }
 
+tracetod()
+{
+    if [ $backend != "dtrace" ]; then
+       echo "DTrace probe generator not applicable to $backend backend"
+       exit 1
+    fi
+    echo "/* This file is autogenerated by tracetool, do not edit. */"
+    convert d
+}
+
+tracetos()
+{
+    if [ $backend != "dtrace" ]; then
+       echo "SystemTAP tapset generator not applicable to $backend backend"
+       exit 1
+    fi
+    echo "/* This file is autogenerated by tracetool, do not edit. */"
+    convert s
+}
+
 # Choose backend
 case "$1" in
-"--nop" | "--simple" | "--ust") backend="${1#--}" ;;
+"--nop" | "--simple" | "--ust" | "--dtrace") backend="${1#--}" ;;
 *) usage ;;
 esac
 shift
@@ -370,6 +539,8 @@ shift
 case "$1" in
 "-h") tracetoh ;;
 "-c") tracetoc ;;
+"-d") tracetod ;;
+"-s") tracetos ;;
 "--check-backend") exit 0 ;; # used by ./configure to test for backend
 *) usage ;;
 esac
-- 
1.7.2.3